1) Field of the Invention
The present invention relates to a technique of monitoring an apparatus to be monitored in a monitoring system using a connectionless communication method (for example, a server system or a network system using an SNMP (Simple Network Management Protocol) trap).
2) Description of the Related Art
Hitherto, in a monitoring (management) system in a server system, a network system, or the like, the SNMP (Simple Network Management Protocol) as a network monitoring (management) protocol employing a connectionless communication method is widely mounted and used.
The monitoring system using the SNMP is constructed by, for example, an apparatus to be monitored and a monitoring apparatus which are connected to each other via a network. At the time of occurrence of an event in the apparatus to be monitored, by transmitting an SNMP trap as event information from the apparatus to be monitored to the monitoring apparatus, the event can be notified to the monitoring apparatus.
However, the SNMP trap is sent by a connectionless communication method conformed with a UDP (User Datagram Protocol) and a communication path is not established prior to communication. Consequently, there is the possibility that the SNMP trap is lost on the communication path (on the network) or on the monitoring apparatus side, and the monitoring apparatus cannot recognize the notification of the event from the apparatus to be monitored.
The SNMP trap is characterized in that, since it is transmitted by communication conformed with the UDP as a connectionless communication method, the SNMP trap can be realized with a relatively simple mechanism and notification can be sent at high speed but, on the other hand, the reliability is low.
To improve the reliability of the SNMP trap, a technique of providing a plurality of monitoring apparatuses, transmitting an SNMP trap from an apparatus to be monitored to each of the plurality of monitoring apparatuses, and inquiring the monitoring apparatuses each other, thereby recognizing loss of the SNMP trap (refer to, for example, Japanese Patent Application Laid-Open No. 2001-67291) and a technique of designating numbers to SNMP traps and checking a drop in the numbers, thereby recognizing loss of an SNMP trap (refer to, for example, Japanese Patent Application Laid-Open No. 2001-160013) are proposed.
However, in the technique disclosed in Japanese Patent Application Laid-Open No. 2001-67291, since the SNMP trap is sent to each of the plurality of monitoring apparatuses, the probability of loss of the SNMP trap can be decreased but there is the possibility that the same SNMP trap cannot reach any of the plurality of monitoring apparatuses. In such a case, the loss cannot be recognized.
In the technique disclosed in Japanese Patent Application Laid-Open No. 2001-160013, in the case where loss of a trap (loss of the SNMP trap) occurs continuously, the loss can be recognized only after loss of the continuous traps is finished, so that it takes time to recognize the initial lost trap. Therefore, in the case where the initial trap in the drop in the continuous traps is a trap related to an event which is important for the system management, the monitoring apparatus cannot recognize the important trap immediately. Thus, it is a problem from the viewpoint of the system management.